DAMP PROOF COURSE

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 Damp proof course 

A continuous layer of impervious damp resisting material provided to protect super structure of a building from dampness. 


Properties of Ideal Damp Proofing Material 

1) Damp proofing material should be impervious for restricting the moisture movement through even a thin layer of it. 

2) It should carry safely the loads coming, over it due to dead weight of the structure , live load , wind load etc. 

3) The material should not change its properties with time. 


Types of Damp Proofing

1) Membrane damp proofing

2)Intergral damp proofing 

3) Surface Treatment for damp proofing 

4) Guniting 

5) Cavity wall Construction 


MEMBRANCE DAMP PROOFING 

By Providing layer or membrance of water repellent material between the source of dampness and the part of structure adjacent to it is called Membrane Damp proofing 

Then this type of layer is called Damp Proofing Course DPC  This layer consists of material like bitumenous felt, mastic asphalt , plastic or polythene sheet and cement concerts erc. The best portion for laying damp proof course in a building without basement is at the plinth level. The D.P.C. can be laid either horizontal or vertically. 

A) Horizontal DPC 

Horizontal D.P.C. consists of cement concerte (1:2:4) with two coats of hot bitumen laid or mastic asphalt it is laid under all walls but not under any opening like doors opening, verandah opening etc. 

B) Vertical D.P.C. 

Vertical dpc is provided on the inner sides of all the outer walls of the building. It may be noted that no vertical DPC is provided on the inner walls. Vertical DPC consists of 15 to 20 mm thick cement plaster 1:3 with two coats of hot bitumen or mastic asphalt. Depth of vertical DPC us 300 mm minimum 

C) Integral Damp Proofing 

Adding certain water proofing compounds in concrete mix to increase its permeability is called Intergral damp proofing 

D) Surface Treatment 

The filling of the pores of the surface ny a thin layer of water repellent material is called Surface treatment. 

Such water repellent material are metallic soaps such as calcium and aluminum oxilates and stearates. Bitumenous solution , cement coating , treatment coating, paints and varnishes also fall under this category . 

E) Guniting 

The spraying a mixture of cement and water or cement and sand with a cement gun is called Guniting

The ratio of cement and sand mixture may be kept as 1:3 or 1:4 

F) Cavity wall 

A wall made up of two separate walls  constructed parallel to each other with a continuous gap 50 to 100 mm wide between then is called a Cavity or Hollow wall.

  The gap does not allow the dampness to enter in the inner wall. Cavity wall has its inner wall as thick wall which supports the load of roofing and floor. The outer wall, also known as outer leaf , has a thickness of 100 mm and it does not allow the dampness to enter in the inner wall. The two walls are connected together with metallic or terracotta tics for obtaining structural stability. These ties are spaced at 900 mm apart horizontal and 300 to 500 apart vertically. 






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